Cutting tools for shredding material usually have a rotary body structure formed with essentially axially extending grooves into which cutter bits, for example in strip form, can be inserted, and held in the grooves, for example by clamping arrangements. The cutter bits should be replaceable since they wear. Usually, the direction of the cutter bits or strips is slightly inclined with respect to the axis of rotation of the tool, for example by about 2.degree.-3.degree..
The cutter bits or strips are usually made of ceramic, stellite, or hard metal. The cutter bits or strips are subjected to high wear, particularly when comminuting or cutting plastics which have been reinforced, for example by reinforcing fibers. It is therefore necessary to so construct the rotary cutter that the cutting elements themselves can be replaced so that sharpened edge portions of the cutters, or the cutter bits themselves, can be replaced as needed.
Many types of cutter bodies and cutter elements are known. The cutter elements are customarily clamped in the cutter body structure. One clamping arrangement utilizes a clamping system in which a cutter bit or strip is pressed against a longitudinal wall of the groove in which the cutter bit is inserted, acting on the cutter element so that the side wall of the grooves is pressed on the cutter element counter the direction of rotation. This provides for effective holding of the cutter bits; yet, the cutting forces acting on the cutter bits are directed counter the direction of clamping forces so that the clamping forces initially applied must be very high.
Superficially, comminuting cutters, and particularly comminuting cutters for plastic material, are somewhat similar in cross section to groove milling cutters. U.S. Pat. No. 3,887,975 Sorice et al describes a groove milling cutter. Contrary to comminuting tools, however, groove mill cutters have axially narrow cutter inserts or cutter chips. The referenced U.S. Pat. No. 3,887,975 shows cutter inserts which can be turned over, so as to provide two cutting edges, which are somewhat parallelogram-shaped, and located, uniformly spaced, about the circumference of a circular disk in recesses having parallel walls.
The leading wall of any recess, with respect to the direction of rotation of the groove mill, receives an eccentric which can be turned into the groove or recess, and which engages in a correspondingly shaped recess in the cutter insert. Due to the narrow width of the cutter inserts, the forces applied thereto will be different from forces acting on axially elongated cutter strips.
The cutter chips of the groove milling cutter are radially clamped with a free surface, not having cutting action, against the bottom of the recess or groove. If the portion of the cutter blade which is engaged with the bottom of the groove previously was an active cutting edge which has been worn, the radial position of the then outermost cutting edge will be different from that if a new chip is inserted. Thus, the radial position of the outermost cutting edge is not independently determined, and turning-over the cutter chip may place the chip in such a position that the outer edge of the turned-over chip is not on the same cylindrical theoretical surface of new cutter chips which have not been turned over. As a result, the forces acting on the respective individual cutter chips will be different.